Highlight Publications 2018

Quantifying Polaron Formation and Charge Carrier Cooling in Lead-Iodide Perovskites
Simon A. Bretschneider, Ivan Ivanov, Hai I. Wang, Kiyoshi Miyata, Xiaoyang Zhu, and Mischa Bonn
Quantifying Polaron Formation and Charge Carrier Cooling in Lead-Iodide Perovskites
Perovskite-based solar cells have been reaching record efficiencies. In these solar cells, light is converted into current (i.e., conducting electrons) by liberating otherwise bound electrons in the material. Despite their promise for solar cells, the fundamentals of this excitation process have yet to be fully understood in hybrid organic-inorganic perovskites. When light of sufficient energy hits a perovskite, electrons are generated that typically have excess energy: they are ‘hot.’ Electrons cool rapidly by giving off energy to the material. In perovskites, the electrons further distort the ionic lattice – attracting positive and repulsing negative ions in the lattice: a so-called polaron is formed, an electron ‘dressed’ with a lattice deformation. In our experiments, we follow the generation of (hot) electrons, their cooling and polaron formation in real-time. While the polaron formation time was found to be independent of the perovskite structure, marked variations in hot electron cooling were observed, in dependence on the structure. Our results show what material parameters can be used to tune – and to some extent control – the hot electron cooling process.
© MPI-P (2018)
The generation of conductive charge carriers in perovskites (lattice shown) occurs very quickly.
Beyond the Protein Corona - Lipids Matter for Biological Response of Nanocarrier
J. Müller, D. Prozeller, A. Ghazaryan, M. Kokkinopoulou, V. Mailänder, S. Morsbach, K. Landfester
Beyond the Protein Corona - Lipids Matter for Biological Response of Nanocarrier
It is well accepted that nanomaterials developed as carrier systems need to be well characterized in terms of biological responses. It was shown that proteins adsorb to the surface of a nanomaterial and define its biological identity. However, the presence of other surface-active components of blood plasma and how they interact with nanomaterials has been much less investigated. Thus, this study aims at providing a significant contribution to understanding the interaction mechanism between lipoproteins and nanomaterials. Since lipoproteins transport a high amount of lipids, which are surface-active molecules, the demonstrated interactions can go as far as complete lipoprotein disintegration.
© Elsevier (2018)
Lipoproteins may adsorb onto nanomaterial surfaces involving disintegration and thus present an explanation for an enrichment of apolipoproteins in the protein corona.
Ultra-low voltage high-sensitivity ion detection with current-driven organic electrochemical transistors
Matteo Ghittorelli, Leona Lingstedt, Irina Crăciun, Zsolt Miklós Kovács-Vajna, Paul W. M. Blom & Fabrizio Torricelli
Ultra-low voltage high-sensitivity ion detection with current-driven organic electrochemical transistors
Ions dissolved in aqueous media play a fundamental role in plants, animals, and humans. Therefore, the in-situ quantification of the ion concentration in aqueous media is gathering relevant interest. The fundamental limitation of approaches based on electrochemical transistors is the trade-off between sensitivity, ion concentration range and operating voltage. Here we show a new current-driven configuration based on organic electrochemical transistors that overcomes this fundamental limit. The measured ion-sensitivity exceeds by one order of magnitude the Nernst limit at an operating voltage of only few hundreds millivolts, opening new opportunities for high-performance bioelectronics.
© Nature Communications (2018)
Device structure of an organic electrochemical transistor using as ion-permeable conducting polymer Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) and an aqueous solution of NaCl as electrolyte.
Molecular Firefighting – How Modern Phosphorus Chemistry Can Help Solve the Flame Retardancy Task
Maria M. Velencoso, Alexander Battig, Jens C. Markwart, Bernhard Schartel, and Frederik R. Wurm
Molecular Firefighting – How Modern Phosphorus Chemistry Can Help Solve the Flame Retardancy Task
As polymers carry an inherent risk of fire, the use of flame-retardants is unavoidable. Current legislation, that is the ban of several halogenated flame-retardants, and novel scientific developments have further made the search for new flame-retardants an important topic. This review article describes the current state-of-the-art of phosphorus-based flame-retardants and highlights examples of modern strategies to a sustainable use of phosphorus-containing materials (low molecular weight and polymeric) as flame-retardants. State-of-the-art phosphorus-based flame-retardants and their mode of action are discussed, showing how they affect the properties of the polymer matrix. Future trends for sustainable phosphorus sources are discussed as well.
© Wiley VCH (2018)
Halogenated and phosphorus-based flame-retardants: How modern phosphorus chemistry can help to establish a sustainable future for flame-retardants.
Saturation of Charge-Induced Water Alignment at Model Membrane Surfaces
Lisa B. Dreier, Yuki Nagata, Helmut Lutz, Grazia Gonella, Johannes Hunger, Ellen H.G. Backus, Mischa Bonn
Saturation of Charge-Induced Water Alignment at Model Membrane Surfaces
The primary building blocks of biological membranes are lipids. The water molecules present at these membrane interfaces are oriented by the charged headgroups of the lipid molecules. A combined theoretical and experimental approach shows that there is a critical charge density above which the water molecules stop responding to the increase in charge. The insensitivity of the water molecules to the increase in charge can be traced to molecular rearrangement occurring at the lipid interface, in combination with the adsorption of counterions. These findings have important implications for reactions occurring at biological membranes.
© MPIP (2018)
Water molecules at negatively charged and net neutral lipid monolayers
On-Surface Synthesis of Indenofluorene Polymers by Oxidative Five-Membered Ring Formation
Marco Di Giovannantonio, José I. Urgel, Uliana Beser, Aliaksandr V. Yakutovich, Jan Wilhelm, Carlo A. Pignedoli, Pascal Ruffieux, Akimitsu Narita, Klaus Müllen, and Roman Fasel
On-Surface Synthesis of Indenofluorene Polymers by Oxidative Five-Membered Ring Formation
On-surface synthesis is a successful approach to the creation of carbon-based nanostructures that cannot be obtained via standard solution chemistry. In this framework, we have established a novel synthetic pathway to one-dimensional conjugated polymers composed of indenofluorene units. Our concept is based on the use of ortho-methyl groups on a poly(para-phenylene) backbone. In this situation, surface-assisted oxidative ring closure between a methyl and the neighboring aryl moiety gives rise to a five-membered ring. The atomically precise structures and electronic properties of the obtained indenofluorene polymers have been unambiguously characterized by STM, nc-AFM, and STS, supported by theoretical calculations. This unprecedented synthetic protocol can potentially be extended to other polyphenylenes and eventually graphene nanoribbons, to incorporate five-membered rings at desired positions for the fine-tuning of electronic properties.
© ACS (2018)
Synthesis of indenofluorene polymer from 4,4"-dibromo-2,2"-dimethyl-1,1':4',1"-terphenyl on Au(111) surface and visualization by noncontact atomic force microscopy (nc-AFM).
 
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